The Purpose of this grant is to fund the Statistical Coordinating Center for the Prospective Evaluation of Radial Keratotomy (PERK) study to examine the patients at ten years after surgery. Radial keratotomy is the most frequently done refractive corneal surgical procedure; approximately 150,000 cases are being done annually in the United States and hundreds of thousands more worldwide. It is important to document the efficacy, safety. stability. and predictability of the procedure over the long-term. The rationale and specific research questions of this study are given in the application for the Clinical Coordinating Center. The Statistical Coordinating Center will be responsible for the following tasks to prepare for and carry out the collection. analysis, and interpretation of the 10 year followup data: (1) maintain current PERK study data; (2) maintain patient information data for tracking and contacting PERK patients; (3) collaborate in the development of the protocol for the 10-year examination; (4) prepare for the training of data coordinators for the nine clinical centers; (5) develop and test data collection forms and procedures; (6) enter, verify. edit and update the data from the clinical centers; (7) prepare reports on clinical performance and patient status; (8) prepare presentations and manuscripts of the study results; (9) plan and carry out the closeout of the clinical centers; (10) if warranted. based on the results of the 10 year examination, make initial preparations for a subsequent 15 year examination of the patients in the PERK study.